Method of making ophthalmic lens



Sept. 5, 1967 F ET AL METHOD OF MAKING OPHTHALMIC LENS 3 Sheets-Sheet 1Original Filed June 7, 1961 l NVENTOI2$ ROBERT E. GEQF BY Bose/er w.OUNG QT ORNEY'S RJE. GRAF ET AL METHOD OF MAKING OPHTHALMIC LENS Sept.5, 1967 v Original Filed Jun: 7, 1961 I5 Sheets$heet 2 l NV ENTORS208687 5. Gem-- 205527 w.

Y You/v6 w (@352 k ATTORNEYS Sept. 5, 1967 GRAF ET AL 3,339,318

- METHOD OF MAKING OPHTHALMIC LENS Original Filed June 7, 1961 I 0 0 i 0O Q Q 3 Sheets-Sheet 5 lNvENTOEs ease/2T 5. GRFIF BY E0552?" w. ou/v5 WWm i'w United States Patent Claims. (Cl. 51284) ABSTRACT OF THEDISCLOSURE A method of treating shoulder surfaces between distanceviewing and near viewing fields of one piece multifocal lenses to directat least the major portion of light striking the shoulder surfaces awayfrom a wearers eyes.

This application is a division of applicants copending application Ser.No. 115,487 filed June 7, 1961, now abandoned.

The field of this invention is that of multifocal ophthalmic lenses, andthe invention relates, more particularly, to novel and improved,one-piece, multifocal lens units and to novel and improved methods ofmaking the same.

It is an object of this invention to provide novel and improved methodof making one-piece multifocal lenses including both bifocal lenses andtrifocal lenses having lens surface portions of different surfacecurvature defining focal fields of different optical power and havingsteps or shoulders separating said surface portions treated so as tosubstantially reduce direct transmission of light therethrough.

Other objects, advantages and details of the method of lens manufactureprovided by this invention appear in the following detailed descriptionof preferred embodiments thereof, the detailed description referring tothe drawings in which:

FIG. 1 is a perspective view of a one-piece multifocal lens blank of thetype with which this invention is concerned;

FIG. 2 is a section view along lines 22 of FIG. 1;

FIG. 3 is a partial section view to enlarged scale similar to FIG. 2;

FIG. 4 is a partial section view similar to FIG. 3 illustrating a stepin the method of lens manufacture provided by this invention;

FIG. 5 is a partial section view similar to FIG. 3 illustrating asubsequent step in said method of lens manufacture;

FIG. 6 is a partial section view similar to FIG. 3 illustrating oneembodiment of the multifocal lens unit provided by this invention;

FIG. 7 is a partial section view similar to FIG. 4 illustrating anintermediate step in a method provided by this invention formanufacturing another embodiment of the multifocal lens unit of thisinvention;

FIG. 8 is a section view similar to FIG. 7 illustrating a subsequentstep in the method of FIG. 7;

FIG. 9 is a partial section view similar to FIG. 5 illustrating afurther subsequent step in the manufacture of said other embodiment ofthe lens unit of this invention; and

FIG. 10 is a partial section view similar to FIG. 6 illustrating saidother embodiment of the lens unit provided by this invention.

Referring to the drawings, 10 in FIG. 1 illustrates a one-piece bifocallens blank of a type well known in the ophthalmic art, the blank beingformed of ophthalmic crown glass or other transparent lens material incon- 'ice ventional manner. One side of a lens blank of this type isprovided with two surface portions 12 and 14 of different surfacecurvature and the surface portions are separated by a step or shoulder16 which preferably but not necessarily extends transversely across theblank in a substantially straight line as shown. In a typical one-piecemultifocal lens blank, for example, the lens surface portion 12 can beprovided with a spherical surface curvature of relatively long radius 18and the surface portion 14 of the blank can have a spherical surfacecurvature of relatively short radius 20, the centers of curvature ofsaid lens surface portions preferably lying along a common axis 22 forestablishing the optical centers of the respective focal fields of theultimate lens, which in the present instance will be in monaxialrelation. The plane of the shoulder 16 also preferably intersects theoptical centers of the focal fields and extends parallel to the axis 22as shown in FIG. 2. The step or shoulder preferably has a minimum heightat the center of the blank sufficient to provide a ledge or step betweenthe surface portions 12 and 14, and the height of the shoulder increasesat the edges of the blank to an extent determined by the difference incurvature of said surface portions.

In a lens blank of this type, the lens surface portion 12 can define anupper or distance focal field and the surface portion 14 can define alower or reading focal field, each of said surfaces displaying aselected surface power. The lens blank surface 24 can then be providedwith an optical finish and with a surface curvature of selected radius26 complementary to the curvatures of the surface portions 12 and 14 forestablishing the optical powers of the distance and reading fields inaccordance with the prescriptive requirements of a person to be fittedwith said le'ns. Where the lens shoulder extends in a straight lineacross the convex surface of the lens, the distance and reading fieldsof the lens will each have substantial width, but it should beunderstood that any other lens having a step or shoulder separatingsurface portions of different surface power are within the scope of thisinvention.

According to this invention, the lens blank 10 is pro vided in partiallyfinished form with the lens surface portion 12 of relatively largerradius of curvature roughground down to the approximate surfacecurvature to be formed thereon as illustrated. The lens surface portion14, however, is optically finished and polished to the precise curvaturedesired, and the step or shoulder 16 is formed in the desired plane forseparating said lens surface portions. A lens blank can be partiallyfinished in this manner by any conventional means but is preferablyfor-med in the manner disclosed in U. S. Patent No. 2,966,767 whichissued to John H. Kress on Jan. 3, 1961.

It will be noted that, where the plane of the step or shoulder 16 passesthrough the optical center of the lens blank parallel to the axis 22 asshown in FIG. 2, the plane of the shoulder will be disposed generallyedgewise to the line of sight of a person fitted with the lens so thatthe shoulder will appear infinitely thin and will not tend to block orinterfere with any part of the wearers field of view. However, anyconventional means employed for optically finishing the lens surfaceportion 14 and for forming the shoulder 16 will tend to form a smallfillet 16.1 of finite width at the junction of the base of the shoulder16 and the surface portion 14. For example, where the blank 10 ismounted upon a lens block 25 by means of pitch 27 or the like and wherean abrading tool 28 is adapted to rotate in the direction of the arrow30 as shown in FIG. 3 for finishing the lens surface 14 and for formingthe shoulder 16, the tool will generally have at least a small radius orchamfer 28.1, or will rapidly wear to form such a radius, so that thetool will not be adapted to remove the fillet 16.1 at the junction ofthe shoulder and the surface 14. Further, where the radius 28.1 on theshoulder-forming tool is very small, as will be preferred, the radiuswill rapidly wear to increase its size so that the fillet 16.1 formed bythe tool upon a series of lenses will tend to vary to a certain extent.As will be understood, even though the fillet 16.1 is very small, thefillet will block or interfere with the field of vision of a personwearing the lens at least to a limited extent and, further, lightreflected from the shoulder 16 as well as the fillet 16.1 will tend todistract the wearers vision.

According to this invention, the surface of the shoulder 16 and theshoulder fillet 16.1 and preferably a narrow strip of the surface 14adjacent the base of the shoulder 16 are treated for substantiallyreducing the direct transmission of light therethrough. For example, theoptically finished surface portion 14 can be masked by any conventionalmeans so that substantially all of said surface portion is provided witha protective shield. The masking means can comprise tape 31 which can bedisposed upon the surface 14 in overlapping relation as shown in FIG. 4,but, if desired, any other masking means such as shellac or aconventional strippable coating or the like can be applied to thesurface 14 for protecting its optical finish. Further, if desired, thelens blank 10 can be disposed in a jig or the like having means adaptedto cover the portion of the blank to be masked as will be understood. Inany event, the masking means 31 should be arranged so that the shoulder16 and preferably a narrow strip 14.1 of the surface 14 adjacent thebase of the shoulder 16 are exposed to view. The strip 14.1 can be of aselected width within a limited range but is preferably at least wideenough to assure that the entire fillet 16.1 is exposed to view. On theother hand, the strip 14.1 should be kept very narrow for a reason whichwill be more fully explained below.

A fine abrasive material 32 can then be directed upon the shoulder orstep 16, and preferably also upon an exposed strip 14.1 of the surface14, at relatively high pressure for providing said surface areas with auniformly textured layer or finish 35 thereon. For example, a finecorundum abrasive (A1 of a particle size of approximately 27 microns canbe blown from the nozzle 34 against said surface areas for providingsaid areas with a textured surface layer 35 similar to that providedupon a very finely ground glass viewing screen. The particles ofabrasive may be blasted against the described surface areas in eiitherwet or dry form as desired. As will be understood, the tape or othermasking means 31 will protect the optically finished portions of thesurface 14 which are masked by said means, and the surface portion 12 ofthe lens blank, which has thus far been finished only to a rough groundstate, will not be adversely affected by action of the abrasivematerial. Thereafter, the abraded strip of the surface 14 and thesurface of the shoulder 16 can be cleaned in any conventional manner.For example, the abraded surfaces can be blown clean with compressed airand can be brushed for removing partially-loosened particles of the lensmaterial.

If desired, the uniformly textured layer 35 provided upon the shoulder16, and preferably also upon the narrow strip 14.1 of the lens surfaceportion 14, can form the final finish layer provided thereon. Forexample, after abrasion of the surface of the shoulder 16 and the strip14.1, the tape or other masking means 31 can be removed from the lenssurface portion 14 and the surface 14 can be cleaned. The lens surfaceportion 12 of the blank can then be optically finished in a conventionalmanner. For example, the blank can be remounted upon a larger block 25.1with pitch 27.1 in the manner shown in FIG. 5 and the surface 12 can beground to its final surface curvature and can be polished with arotating tool 37 in the manner described in the previously noted U.S.patent.

The multifocal lens unit 39 provided by the abovedescribed process isshown in FIG. 6. As illustrated, the shoulder 16 of the lens unit willhave a layer 35 thereon similar to that found upon the surface of aground glass viewing screen, the textured layer 35 preferably extendingover a narrow strip 14.1 of the reading portion of the lens unit. Inthis construction, the surface areas treated as above described areadapted to substantially reduce the direct transmission of lighttherethrough and are adapted to avoid formation of a coherent anddistinguishable band of light reflected from the shoulder 16 or theshoulder fillet 16.1. That is, as shown in FIG. 6, light rays such asthe rays 41 and 43 which are incident upon the shoulder 16 and theshoulder fillet 16.1 and which, in a conventional one-piece multifocallens, would tend to be uniformly reflected from the shoulder and filletto form a coherent band of refiected light, will be diffusely reflectedand refracted or scattered at the surface layer 35. Thus some of thislight will be reflected away from the eye of a person fitted with thelens unit as indicated in FIG. 6 by the light ray 41, whereas otherlight reflected or refracted toward the eye from the layer 35 will be sodiffused and scattered as to prevent distraction of the vision of aperson fitted with the lens unit.

In a preferred embodiment of this invention, the lens blank 10 isprocessed in the manner described above with reference to FIGS. 1-4.Then with the tape or other masking means 31 remaining in shieldingrelation to the lens surface portion 14, a thin coating or layer oflightabsorbing material 36 can be applied to the shoulder 16 andpreferably to the narrow strip 14.1 of the lens blank as shown in FIG.7. The light-absorbing material 36 can be applied either by spraying, asis preferred, or by painting or by other conventional techniques, theuniform texture of the ground surface layer 35 tending to accept acoating of light-absorbing material of uniform thickness. For example,the light-absorbing material 36 can be sprayed from a nozzle 45, asshown in FIG. 7 for applying a coating 36 which may extend partiallyover the masking means 31 and partially onto the lens surface portion12.

The light-absorbing material 36 which is applied to the abraded surfaceareas of the lens blank 10 can be any one of a great many well-knownmaterials which are adapted for this purpose. For example, thelight-absorbing material can comprise any of the light-absorbingsolderlike glasses which can be applied to the abraded blank areas in amolten state. Alternatively, the light-absorbing material can compriseone of various noble metals which can be deposited upon the abradedblank areas by any conventional technique. For example, a noble metalcarried in dispersion in an organic medium can be sprayed onto theabraded blank areas and can be subsequently heated for burning off theorganic medium and for leaving a coating of the metal deposited on saidblank surface areas. A preferred light-absorbing material which can beemployed for the puropses of this invention comprises one of thevitreous enamels or lusters such as those which are manufactured by theHanovia Chemical Company of East Newark, N]. For example, the vitreousenamel commercially known as Ruby Lustre No. 7828 can be sprayed fromthe nozzle 45 onto the abraded blank surfaces previously described andcan be allowed to dry. Preferably several coats of the luster can beapplied to provide a relatively dark coating which is adapted forapproximately percent absorption of light incident thereon.

When the light-absorbing luster 36 has dried, the tape 31 or othermasking means can be removed as shown in FIG. 8, and the opticallyfinished surface 14 is preferably cleaned. The lens blank 10 can then bedisposed upon a ceramic block 38 or other suitable support and can beplaced in a furnace of any suitable type such as is diagrammaticallyindicated by the heating coil 40 and the support 42 for firing thecoating 36 Where required. Where the Ruby Lustre of the type abovedescribed is utilized, for example, the luster can be fired at atemperature between 850 F. and 1050 F. for fusing the luster to the lensmaterial. However, where the lens blank is formed of an ophthalmic crownglass having a strain point of approximately 960 F. for example, theluster is preferably fired at a temperature of approximately 950 F. fora period of approximately 5 minutes to avoid establishment of stressesand distortions in the blank. On the other hand, if the selectedlight-absorbing material is to be fired at a temperature above thestrain point of whatever material is embodied in the lens blank 10, thelens blank can be thereafter annealed in conventional manner. Forexample, where the noted ophthalmic crown embodied in the blank 10 hasan annealing temperature of about 1030 F. and where the light-absorbingmaterial 36 is fired at a temperature of 1050 F., the lens blank can beannealed by slowly cooling the blank through an annealing cycle from thetemperature 1030 F. to a temperature of 960 F. in well known manner.

After the light-absorbing material 36 has been fused or otherwisesecurely adhered to the lens blank 10, the lens surface portion 12 ofthe blank can be optically finished in conventional manner. For example,the blank can be mounted upon the larger lens block 25.1 with pitch 27.1as shown in FIG. 9 and can be abraded and polished by a rotating tool 44in the manner described in the previ ously noted US. patent. In theprocess of optically finishing the lens surface portion 12 byconventional techniques, any of the light-absorbing material 36 whichmay have been applied to that surface will be removed as will beunderstood.

The multifocal lens unit 46 provided by the abovedescribed process isshown in FIG. 10. As illustrated, the shoulder 16 of the lens unit willhave a coating of lightabsorbing material thereon, the coating extendingdown over a narrow strip of the lens surface portion 14 to an extentsufiicient to cover at least the shoulder fillet 16.1. In thisconstruction, light rays such as the ray 48 which would tend to beincident upon and reflected from the shoulder 16 into the eye of aperson fitted with the lens unit will be substantially completelyabsorbed by the coating '36 as shown in FIG. 10. Even light rays such asthe ray 50 which impinge upon the coating 36 at grazing incidence andwhich are therefore at least partly reflected from the coating will tendto be intercepted and absorbed by that part of the coating 36 whichextends down over the surface 14.

It has been noted previously that the occurrence of a fillet 16.1 atthejunction of the shoulder 16 and the lens surface 14 is, as a practicalmatter, unavoidable in manufacture of a lens of the type and that such afillet will tend to provide a degree of distortion in that part of afield of vision viewed through the fillet. However, where the fillet iscoated with a light-absorbing material in the manner above-described andwhere the coating 36 does not extend very far below the fillet onto thelens surface 14, no distorted light rays can be transmitted through thefillet to distract the vision of a person fitted with the lens unit 46,and yet the field of clear vision obtained with the lens unit will notbe significantly smaller than that which can be obtained withconventional one-piece multifocal lenses.

Further, it can be seen that the shoulder 16 cannot be completelyconcealed from view in a one-piece lens of this type, and it will beunderstood that the junction of the shoulder 16 with the lens surfaceportion 12 as at 16.2 will be subject to fi-aking or chipping and willappear quite fragile. However, where the coating 36 applied to theshoulder 16 comprises a Ruby Lustre or the like as previously suggested,the shoulder can form a pleasing line across the lens enhancing theappearance of the lens unit and providing a desirable cosmetic effect tothe lens. In addition, the coating 36 will reduce the fragile appearanceof the junction 16.2 and will provide at least a limited degree ofprotection for said junction for preventing flaking or chipping thereof.

Although the process for preparing a lens unit according to thisinvention has been described above with application to a bifocal lensunit, it will be understood that trifocal lenses and the like could alsobe prepared according to this invention. For the manufacture of trifocallenses, a light-absorbing coating would be applied to the shoulderbetween the reading and intermediate portions of the lens blank beforethe intermediate portion of the blank is optically finished. Then thesecond shoulder of the blank would be coated with light-absorbingmaterial after optical finishing of said intermediate lens portion andbefore optical finishing of the distance portion of the blank as will beunderstood.

It should also be understood that the bifocal lens blank has beendescribed by way of illustration and that this invention includes allmodifications and equivalents, of the described lens unit and method oflens manufacture which fall within the scope of the appended claims.

Having described our invention, we claim:

1. A method of making an ophthalmic lens unit of the characterdescribed, said method comprising the steps of providing -a lens blankhaving a side which is divided into at least two portions of differentsurface curvature and having a shoulder surface extending between saidportions, the surface curvature of at least one of said portions beingoptically finished, masking said optically finished surface curvature atleast adjacent to said shoulder surface, treating said shoulder surfaceto adapt same for substantially reduced light transmission therethroughand removing said mask from said finished surface portion.

2. A method of making an ophthalmic lens unit of the characterdescribed, said method comprising the steps of providing a lens blankhaving a side surface which is divided into at least two surfaceportions of different surface curvature and having a shoulder extendingbetween said surface portions, the surface portion of shorter radius ofcurvature being optically finished, masking substantially all of saidfinished surface portion other than a narrow strip thereof of selectedwidth extending along said shoulder, blasting said shoulder and saidunmasked strip of the finished lens surface portion with abrasivematerial for forming a uniform, finely ground finish thereon, removingsaid mask from said finished surface portion, and optically finishingthe other of said lens surface portions.

3. A method of making an ophthalmic lens unit of the characterdescribed, said method comprising the steps of providing a lens blankhaving a side surface which is divided into at least two surfaceportions of different surface curvature and having a shoulder extendingbetween said surface portions, the surface portion of shorter radius ofcurvature being optically finished, masking said finished surfaceportion, applying a coating of light-absorbing material to saidshoulder, removing said mask from said finished surface portion, andoptically finishing the other of said surface portions.

4. A method of making an ophthalmic lens unit of the characterdescribed, said method comprising the steps of providing a lens blankhaving a lens surface which is divided into at least two surfaceportions of different surface curvature and having a shoulder extendingbetween said surface portions, the lens surface portion of shorterradius of curvature being optically finished, masking substantially allof said finished surface portion other than a narrow strip thereof ofselected width extending along said shoulder, blasting said shoulder andsaid unmasked strip of the finished lens surface portion with abrasivematerial for forming a uniform, finely ground finish thereon, applying acoating of light-absorbing material to said shoulder and said strip ofthe finished lens surface portion, removing said mask from said finishedsurface portion, and optically finishing the other of said lens surfaceportions.

5. A method of making an ophthalmic lens unit of the characterdescribed, said method comprising the steps of providing a lens blankhaving a lens surface which is divided into at least two surfaceportions of different surface curvature and which has a shoulderextending in a straight line transversely across said lens surfacebetween said portions, the lens surface portion of shorter radius ofcurvature being optically finished and being joined to said shoulder bya relatively narrow fillet, applying a masking material to substantiallyall of said finished surface portion other than a narrow strip thereofextending along said shoulder, said strip being of selected width toinclude at least said narrow fillet, blasting said shoulder and saidunmasked strip with abrasive material for forming a uniform, finelyground finish thereon, cleaning said References Cited UNITED STATESPATENTS 1,951,506 3/1934 Duckwall 351-168 2,216,182 10/1940 Boeder et al351170 2,299,405 10/ 1942 Prange 51-310 X 2,847,804 8/1958 Calkins et al351--l77 X 2,963,823 12/1960 Ohliger 351177 X 15 2,966,767 1/1961 Kress51284 LESTER M. SWINGLE, Primary Examiner.

1. A METHOD OF MAKING AN OPHTHALMIC LENS UNIT OF THE CHARACTERDESCRIBED, SAID METHOD COMPRISING THE STEPS OF PROVIDING A LENS BLANKHAVING A SIDE WHICH IS DIVIDED INTO A LEAST TWO PORTIONS OF DIFFERENTSURFACE CURVATURE AND HAVING A SHOULDER SURFACE EXTENDING BETWEEN SAIDPORTIONS, THE SURFACE CURVATURE OF AT LEAST ONE OF SAID PORTIONS BEINGOPTICALLY FINISHED, MASKING SAID OPTICALLY FINISHED SURFACE CURVATURE ATLEAST ADJACENT TO SAID SHOULDER SURFACE, TREATING SAID SHOULDER SURFACETO ADAPT SAME FOR SUBSTANTIALLY REDUCED LIGHT TRANSMISSION THERETHROUGHAND REMOVING SAID MASK FROM SAID FINISHED SURFACE PORTION.